Histopathology of pityriasis rosea Gibert. Qualitative and quantitative light-microscopic study of 62 biopsies of 40 patients.

62 biopsies of 40 patients with pityriasis rosea Gibert (PRG) were analyzed qualitatively and quantitatively. The main histopathological feature is eczematoid. In addition, the following characteristics, especially in combination, are helpful for the differential diagnosis: absence or decrease of the granular cell layer, erythrocytes in the papillary dermis and partly in the epidermis, and homogenization of the collagen of the papillary dermis. Recent and older lesions show little difference although the number of eosinophils in the inflammatory infiltrates has generally increased.